Automatic telephone-exchange system.



C. L. GOODRUM.

AUTOMATH) TELEPHONE EXGHANGE $YSTEM. APPLICATION FILED NOV. 18, 191' 1,231,013 PatentedJune 26, 1917.

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APPLICATION man NOV 18, 1914.

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C. L. GOODRUM.

AUTOMATIC TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV. I8. 1914.

1 ,23 1,01 3 Patented June 26, 1917.

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C. L. GOODRUM.

AUTOMATIC TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV 18. 1914.

1 ,23 1 ,Q 1 3 Patented June 26, 1917.

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CHARLES L. GOODRUM, or NEW YORK, N. Y., AssIGNoit, BY"MES1\TE ASSIGNMENTS, T0 wEsr n nLEcraIo COMPANY, INCORPORATED, A conronarro or E YORK.

- AUTOMATIC TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent. Patented June 26, 191 '7.

- Application filed November 18, 1914. Serial No. 872,743.

To all whome'tmayconcern':

Be it known that LCHARLEs L. GooDRUM, a citizen of the ."United States, residing at New York,lin the county of New York and State of New '"York, have invented certain new and useful Improvements in Automatic Telephone-Exchange Systems, of which the following is'a' full, clear, concise, and exact description.

This invention relates to telephone exchange systems employing machine switching.

One of the features of the invention is the provision of a novelfandsimplified circuit arrangement in systems wherein the calling lines are associated'with the connecting circuits by line finders, these line finders being set in motion by the initiation of calls. In

accordance with this feature of the invensaid terminals, the operation of the device of the calllng line actuating means to stop further movement of sald finder arm, where.

by the calling line is connectedt o an extending circuit; J

The ordinary line andcuto-fi relays are preferably employed to control the line finder, the line relay upon its. energization' operating a starting relay Whose circuit leads through an armature and back contact of the associated cutoff relay so that the line finder is stopped upon the energization of the cutoff relay the instant the finder reaches the calling line terminals. t

Another feature of the invention relates to starter wire systems wherein the starter wire is led through off-normal contacts associated with busy finders to the neXt idle finder, and consists in the provision of a circuit arrangement wherein, when the starter wire circuit to such finder is closed, the continuity of such-circuit is maintained until such finder connects with the calling line. This may be accomplished by maintaining the release circuits of busy finders open until the finder which has been started reaches the calling line.

Another feature of the invention involves a novel arrangement for releasing all the selector switches except the connector, by means of. a current. impulse over the trunk release wire, when the calling party hangs up his receiver.

A further feature relates to the means for operating the cutoff relay of the called line 1n advance of the application of ringing current to the contacts thereto, to prevent the useless startin'g in operation of. a line finder, and to prevent the premature cutting off of the ringing current due to apossi'ble momentary rush of current through the line relay of the called line.

Another feature of this 1 invention relates to themeans for preventing the cutting off of the ringing current supply through a momentary energization of the marginal ringing cutoff relay due toi'condenser discharge, swinging grounds or crosses, and the like.

Another feature of the invention relates to the means whereby a single condenser is used to prevent's tiarking'ata plurality of contacts.

Otherv features of'the invention will be specifically pointed out in the following detailed description and claims.

Referring-to the drawings Figure 1 shows all of the apparatus individual to one subscribers line and a portion of the apparatus individual to another in the same group, and apparatus common to the entire group of lines, that individual to the lines being shownto the left, and that common tothe group to the right of the dotted line;

-'Fig. 2 shows a line'finder and a first selector. with their associated circuits and ap paratus;

- Fig-'3' showsa final switch or connector and'its associated circuits and apparatus;

- Fig. 4 shows theimanner in which an idle line finder is preselected;

; Fig. 5 isa perspective iew of the lower portion of a suitable finder. switch. for. use with the circuit arrangement of Figs. 1 to 1;

Fig. 6 is a sectional'vi'ew 'on the line '66 ofFig.5; Y

Fig. 7 is a sectional view on the'line 77 of Fig. 5;

Fig. 8 is a detail view of the brush rod rotating means;

Fig. 9 is an enlarged view of the steering or controlling switch shown in Fig. 5;

. and

Fig. 10 is a side view of the upper portion of the finder switch of Fig. 5 and the vertical row of terminals in the panel it is adapted to serve, onesection of the row being fully shown and another partly shown in section, with the cooperating sets of brushes;

act as either a finder switch, a-selector switch or a final selector or connector. The terminal bank is of the type'shown in United States Patent N 0. 1,098,529. It is made up of strips of metal 500 and interposed'insulating strips 501(Fig. 12). Each metallic strip 500 has ears projecting from opposite faces of the panel-and adapted to be wiped over by the brushes of the automatic switchesf Three of these sheets 500 are apportioned to each a line.

A setof terminals 224, 225, 226, one belonging to eachof three adjacent sheets belonging to a given line, is adapted to be engaged by a set of brushes 221, 222, 223 of a line finder switch, to connect with said line on one side of the panel as a calling line, and the opposite projections 502, 503, 504 of the same metal sheets are adapted to be engaged by a. similar set of brushes of a final switch or connector to" connect with said line as a called line. The number of sets of ears or terminals on the three sheets corresponds to the number of finder and connector mechanisms, the number of which is determined by the traffic.

' The panel or bank contains the line and test terminals of one hundred lines, divided horizontally by metal bars 506 into ten divisions or groups of ten each. Thus each e6 enough topermitthe brushes to rotate with? vertical row containing the sets of terminals of one hundred lines is divided into ten sections. Each such section is served by a set of brushes 221, 222, 223 adapted to contact with the sets of terminals 224, 225, 226. These sets of brushes are mounted upon supports 508 which are in turn rigidly mounted upon a common carrier or rod 507. The sets of brushes are spirally arranged upon the brush rod 507, and the rod is first rotated to position the proper set of terminals below the desired section of the vertical row served by said rod, whereupon the rod is elevated, during which movement the selected set of brushes wipes'over the sets of terminals of its section of the row. The bar506 between the sections is made wide outlhindrance by the fixed terminals. The brush rods of the finder switches are so arranged that each section, representing a group of'lines, has one set of brushes nor mally just below the vertical section of the row containing the terminals of said lines, whereby connection is quickly made to any line in such group when calling. However, it is preferable to have all the finders accessibleto all the lines of all the groups, and the circuit arrangement herein disclosed is such that if the finder normally assigned to any group is busy, another finder will be set in motionby the initiation of a call in such group to connect with the terminal of such line. In this eventthe brush rod of the idle finder is given a rotary movement to position the brush serving the section of the vertical row, wherein said group of lines terminates, below said section, and thereafter a vertical movement to connect with the calling line in suchg'roup. For this purpose a switch 509 is located at the top of each finder. Each group of lines is represented on this switch by a metallic segment 265. These segments are adapted to be wiped over by an arm 214 fixed to the brush rod 507. The initiation of a call in any group electrically distinguishes the segment 265 individual thereto on the switch 509 of the preselected finder, so that when the brush 214 reaches such segment a circuit change is brought about to stop such movement, and the relation between the arm 214 of each rod 507 and its sets of brushes is such that when said arm has reached the segment in question, the set of brushes belonging to this line group'is positioned just below thesection of terminals in which this group of lines terminate. 'The upward movement of the rod causes the said set ofbrushesto wipe over the sets of terminals of this section until that of the calling line is reached, when a circuit change is produced to stop such movement, whereby the calling line is connected through this finder to a selector (shown on Fig. 2), which is then controlled from the sender at the substation to extend the connection either to a connector (shown in Fig. 3), or in case of a large exchange first through a series of selectors.

In the event the line finder normally assigned to the group containing the calling line is idle, the arm 214 is in contact with.

the segment 265 individual to said group,

and a circuit change is produced immediately upon the initiation of the call, which causes the rod to move upwardly wiping the brushes over the sets of terminals in the section corresponding to this line group.

Inasmuch vasthe switch structure itself is not claimed herein, only a brief description thereof, necessary for a comprehension of the circuit arrangement forming the subject-matter of this invention, will begiven.

The brush rod 507 is provided near its lower end with a gear wheel 512. The pawl 516 of the armature 517 of rotary magnet 205 does not act directly upon the rotary ratchet 512 of the rod, but steps around a member 519 by engaging a gear wheel 521 thereon, which member carries a second ratchet wheel 520 which meshes with the gear wheel 512 on the rod 507. After the brush rod 507 has been rotated by said magnet to the proper point, the rotary magnet ceases to operate. The rod is then elevated by the pawl 524 carried by armature 523 of vertical magnet 207 mounted upon the frame 514.

Upon the beginning of the upward move ment of the brush rod 507, a spring 525 secured to the frame moves upwardly, a pin 526 thereon entering a notch in the gear wheel 520 to prevent the member 519 from being restored by the spring 527 when the dog 528 is withdrawn later, this dog and the dog 529 of the vertical ratchet being re leased by the attractive movement of the armature 550 of the release magnet 203. A

roller 556 carried by an arm 530 of the release magnet armature 550 moves plate 554, which carries dog 52S, outwardly, an arm 557 on this plate engaging an arm 558 on the plate 555, one of the arms of which is the dog 529 of the vertical magnet.

WVith the construction described, the brush rod 507 drops entirely free when released at the termination of the conversation by the actuation of release magnet 203, and consequent withdrawal of dog 529. When it (reaches its lowermost position the shoulder 53.2 presses the spring 525 against the mounting plate 533. The consequent withdrawal of the pin 526 from the gear wheel 520, permits the spring 527 to rotate the member 519, whereupon the gear wheel 520 restores the brush rod 507 to normal position. a

The steering or control switch is shown most clearly in Fig. 9. The function of this switch is to prepare circuits at the proper times for the control of the automatic selector switches, one of these switches being associated with each automatic switch. arm 535 of the steering switch carries a set of brushes adapted to wipe over a series of contacts 537 arranged in an arc. The arm 535 is held under tension by a spring 538. The arm 535 is released step by step under the influence of said spring by an escapement mechanism controlled by the armature 539 of a magnet 217. This escapement mechanism consists of a member 540 notched on both sides and fixed to the arm 535, and a pair of arms 541, 542 pivoted on the armature pivot pin 543. These two arms tend to move together under the influence of a spring 544.

In the normal position of'the' steering switch the arm 542 is held by spring 544 in engagement with the second tooth 553 on the right-hand side of the member 540 as shown. In this position the brushes 536 are in contact with the first set of contacts of the bank 537. Upon the attraction of the armature of magnet 217, an arm 545 thereof moves arm 542 out of engagement with tooth 553, whereupon the spring 538 moves the arm 535 to cause its brushes to contact with the second set of the bank of contacts 537. The arm 535 thus is stopped by the arm 541 engaging tooth 546. The armature in its retractive movement moves the arm 541 out of engagement with the tooth 546, and the arm 535 moves its brushes to the third set of contacts, the arm 542 catching the tooth 549 and holding the brushes on the third set of contacts. This switch, as will be seen in Fig. 5 is restored by the armature 550 of the release magnet 203, which pulls the dogs 528, 529 from the ratchets of the brush rod 507 to release the same.

The steering switch for the selector differs from that shown in Fig. 9 in the cutting of the teeth of the member 540. In this switch the arm 535 moves from position 1 to 2 upon the retractive movement of the armature of its escapement magnet, and from 2 to 3 on the attractive movement. The steering switch of the connector moves from one position to the next only upon the retractive movement of the armature of its escapement magnet. In other respects the escapement magnets of the selector and connector correspond to magnet 217 of the finder.

Referring now to Figs. 1, 2, 3 and 4, which show the circuit arrangement of this invention, using automatic switches of the type just described the subscribers line conductors 111, 112 terminate in a pair of terminals 224, 225. The usual test terminal 226 is associated with each pair of line terminals, and is connected by a conductor 114 with the cutoff relay 120 of this line. Each subscribers line is provided at the central office with a line relay 116 bridged across the conductors 111, 112, which becomes energized when the subscriber closes the line circuit by removing his receiver. The line and cutofi' relays 131, 132 of another line in the same group are also shown. A number of the finder switches shown in Figs. 5 to 13 proportional to the traflic, would be apportioned to the lines in such a manner that each group would, if no connection exists involving one of the lines of such group, have a line finder so related to the section of terminals of such group in the panel that a set of brushes on the brush rod 507 of such finder would be just below such section, and upon the closure of the circuit of any line in said group would be elevated, causing said set of brushes to wipe over said section of terminals in search of thecalling line. However, if this finder hadbeen taken for use, a call from this group will be taken care of by, the next idle line finder, which, however, must rotate to position the proper set of brushes below thesection of terminals containing the calling line. r U I The invention will be best understood by a detailed description of the operations involved in interconnecting two substations.

When the subscriber at substation 110 removes his receiver, a circuit is closed for the line relay 116, said circuit leading over the line conductors 111 and 112 and through the telephone set of substation 110. This relay thereupon closes a circuit for-relay c to start a finder searching. for this calling line, this circuit leading from the free pole of battery through the left-hand winding of relay 116, left-hand. armature and back contact of the cutoff relay 120, conductor 121, contacts 117, 118, conductor d, lefthand armature and back contact of relay a, conductor 134, relay 0" to ground. Relay a thereupon locks itself up in series with the line relay 116 in a circuit leading through its left-hand armature and front contact,.said circuit being independent of relay a. Relay 0 at its right-hand armature and front contact closes a circuit for the escapement. magnet 217 to move the steering switch of the line finder into position 2 to begin the upward movement of the brush rod to cause the set of wipers-0f this line group to test for the calling line, assuming that the line finder normally associated with the starter wire 130 is not in use. Under such assumption the arm 214 of the finder brush rod is in contact with metallic segment 265 individual to this line group. This circuit is as follows: free pole of battery, magnet 205 (Fig. 2), conductor 212, magnet 217, conductor 218, arm 216, conductor 215, arm' 214, segment 265, conductors 130, 127, right-hand armature and front contact of relay 0 to ground. 'The magnet 205 is so adjusted and the circuit conditions are such that it does'not operate when this circuit is closed. The magnet 217 upon its energization moves the steering switch to position 2, in which position the circuit for the said magnet 217 is maintained, this circuit being as follows: free pole of battery, magnet 205, conductor 212, magnet 217, conductor 218, arm 216, now in position 2, conductor 287, iconductors 202, 201, arm 200, conductor 129, righthand armature and front contact of relay 7), conductors 128, 127, right-hand armature and front contact of relay 0 to ground. The-relay b was energized upon the energization of relay 0, and is made slow-acting fora purpose set forth later,

The arm 210 of thesteering switch in position 2 closes a circuit for magnet 207, which Cutoff relay by interrupting its own circuit raises the brush rod, during which movement the set of brushes wipes over the group containing thecalling line. This circuit is as follows: free pole of the battery, secondary magnet 207, conductor 219, arm .210 and its second contact, conductors 209, 208, armature and backcontact of magnet 207, conductors 268, 266, right armature and front contact of magnet 217, conductor 267, conductor 204, armature and back contact of release magnet 203, conductors 202, 201, arm 200, conductor 129, right-hand armataure and front contact of relay 6, conductors 128, 127, right-hand armature and front contact of relay 0 to ground. When the brushes 221, 222' and223- arrive upon the terminals 224, 225 and 266, representing the line of the subscriber initiating the call, the cutofl relay 120 of such line is energized over the following circuit: free pole of the battery, relay 120, conductor 114, terminal 226, brush 223, conductor 113, contacts 228, 270 of magnet 217, conductor 271, resistance 272, conductor 201, arm 200, conductor 129, right-hand armature and front contact of relay 6, conductors 128, 127, right-hand armature and contact of relay 0 to ground. 120 at its left-hand armature opens the circuit of relay 0, which in denergizing opens the circuit of driving magnet 207, the finder being thus brought to rest upon the calling line terminals,and held there by holding pawls 528, 529 (Figs. 5 and I 10'). When the cutoff relay 120 operates and de'c'nergizes the relay 0 the escapement magnet 217 also is deenergized, whereupon the steering switch moves to position 3. The closure of contacts 228, 229 of magnet 217 puts ground on the multiple test terminals of this line, whereby connection cannot be made to it by a connector. In this position the arms 232 and 233 of the steering switch connect the line conductors 111, 112 through tothe line relay 234 of the selector. It will, of course, be understood that the operations involved in connecting the calling line with a connecting -circuit just traced take only a fraction of a second. The line relay 234 at its armature and-front contact closes a circuit'for a slow-acting relay 235. The subscriber will now operate his sender. The relay 234 is adjusted to respond to each interruption of the line circuit, but the relay 235 is arranged to remain energized during such interruptions. Each time the armature of the relay 234 closes its back contact, an impulse isgiven to the rotary driving magnet 236 to cause the brush rod 507 of the first selector to be rotated to position the proper'set of brushes below the group of trunks terminating in connectors serving the desired group of subscribers. This circuit is. as follows: free pole of battery, magnet 236, conductor 269, contact 237 causes the slow-acting relay 240 to become denergized. It will be noted that this relay was energized upon the first denergization of relay 234 by a circuit leading through armature and front contact of slow relay 235. The relay 240 at its front contact closed a circuit for the escapement magnet 241 of the steering switch of the selec tor, which, however, did not permit the steering switch to move. Upon the reclosure of the line circuit for a relatively long interval after the interruptions correspondin g to the hundreds digit of the line wanted have been sent, the line relay 234 is maintained energized, whereupon the relay 240 is de'energized, thus opening the circuit of escapement magnet 241. This permits the steering switch to move to position 2 to cause the set of brushes 246, 247,248, which has thusbeen positioned, to hunt over the group of trunks for anidle connector. As soon as the steering switch arrives in position 2, a circuit is closed for the vertical driving magnet 242 of the selector, this circuit being as follows: free pole of battery, magnet 242 and its armature and back con tact, steering switch arm 243 and its second lay 305 to ground.

contact, conductor 244, conductor 245, armature and front contact 'of relay 234 to ground. The magnet 242 thereupon makes and breaks its own circuit, thus causing the brushes 246, 247 and 248 to wipe over the fixed contacts 249, 250 and 251. An idle trunk is represented by ground on the test contact 251 thereof. Therefore, when the test brush 248 reaches the contact 251 of an idle trunk, a circuit is closed from the free pole of battery, ,escapement magnet 241, arm 252 and its second contact, conductors 253, 254, brush 248, test contact 251, conductor 255, left-hand armature and-back contact of relay 301, conductor 302, right-hand armature and back contact of relay 303, conductor 304, armature and back contact of re- Thereupon the escapement magnet 241 is energized and permits the steering switch to move to position 3, the arm 243 opening the driving circuit for the vertical magnet 242, to stop the brushes on the idle trunk thus selected.

As the steering switch moves into position3, its arms 256, 257 extend the calling line circuit through to the connector, shown.

on Fig. 3. The relay 305 thereat, which is the stepping line relay, immediately becomes energized, and at its armature and front contact closes a circuit for a slow-acting relay 303. The interruptions of the line circuit now caused by the subscriber operating his sender to select the tens digit of the wanted line, cause impulses to be sent to the rotary magnet 306 of the connector, which positions the proper brush below the group containing the desired line. The circuit is as follows: free pole of the battery, magnet 306, conductor 308, arm 3099, conductors 310, 311, right-hand armature and front contact of slow relay 303, conductor 304, armature and back contact of relay 305 to ground. It will be understood that rclay 303 like relay 235 of the selector remains energized during the line interruptions corresponding to the tens digit. It will be noted that upon the en-ergization of the slow relay 303 and the first deenergization of relay 305 in sending the tens digit, slow relay 312 became energized, and closed at its righthand armature and front contact a circuit for the escapement magnet 313 of the steering switch, which, however, does not release the steering switch except upon its de'e'nergization. Therefore, when the line circuit becomes closed upon the termination of the interruptions corresponding to the tens digit, the slow relay 312 becomes deenergized and the escapement magnet releases the steering switch into position 2. The arm 309 thereupon substitutes the vertical magnet 307 in place of the rotary magnet 306, in the stepping circuit. The interruptions corresponding to the units digit thus operate this vertical magnet in the following circuit; free pole of battery, magnet 307, arm 309 and second contact, conductors 310, 311, right-hand armature and front contact of slow relay 303, conductor 304, armature and back contact of the line relay 305 to ground. The slow relay 303 remains energized during the short interruptions of the line circuit corresponding to the units digit, as in the operation of sending the tens digit. As before, the slow relay 312 was again energized upon the first deenergization of the line relay 305 and energized the escapement magnet 313. Upon the cessation of the interruptions of the line circuit corresponding to the units digit, the slow magnet 312 becomes deenergized and the escapement magnet 313 releases the steering switch. In case such line is busy, a ground will be present upon the test terminal 314, and a circuit will be completed from the said test terminal to the release magnet 317 of the connector before the steering switch escapement magnet can become de'energized to permit the steering switch to move out of position 2, the escapement magnet 313 being made slow acting for this purpose. Thus. in case the selected line is busy when the test brush 315 of the connector reaches the test contact 314 thereof, a circuit is Closed from ground either at arm 318 and its fourth contact of some other connector,

if such line is busy as :1 called line, or from ground at the back contact of release magnet 203 (Fig. 2) if such line is busy as a calling line. Thus incase the line is busy a circuit for release magnet 317- is closed leading from said grounded test contact 214, brush 315, conductor 316,v arm 318 and its second contact, conductor 319, armature and back contact of relay 312, conductor 320, oil'- 7 normal contact 321 closed upon the first r tar'y step of the brush rod, conductor 322,

armature and back contact of relay 301, conductor 346, right-hand winding of release magnet 317, to the free pole of battery. The

release magnet thereupon withdraws the holding pawls 528, 529 of the connector, which restores itself and its steering switch;

The release magnet upon its energization closes a locking circuit for itself from ground through its left-hand high-resistanoe' Winding, its left-hand armature and front contact, conductor 223, left-hand ar mature and front contact ofrelay 303, conductor 324, conductor 255, contact 251,brush 248, conductor 254, arm 258 and third contact, conductor 259, off-normalcontact- 260, release magnet 261 of the selector to free pole of battery; a circuit in parallel withthis leads from free pole of battery, release magnet'203 of the finder, off-normal contact 262, conductor 263, right-hand armature and back contact of relay a, conductor 264, conductor 259 to ground, through the high-resistance winding of the release magnet of the connector. The resistance of the left-hand winding of the release magnet 317is made highenoughrto prevent the op eration of release magnets 203 and 261.

The releasemagnet 317 at its right-hand armature and front contact connects a busy back apparatus 325 to the conductor 326, thus indicatingto the calling party that the desired line is busy. When the calling subscriber replaces his receiver, the high-resistance winding of the release magnet 317 is shunted by the falling backof theleft hand armature of the relay 305, whereupon the release magnets 261 and 203 receive enough current for their energization, and

withdraw the holding pawls to restore the selector and line finder, which in restoring restore their steering switches. The hanging up of the calling partys receiver causes the release magnet 317 of the connector to become deenergized by the opening of its circuit at the left-hand armature and front contact of slow-acting relay 303, whereupon the'busy back circuit is opened. All the apparatus is now in its normal position.-

If, on the other hand, the desired line is free, the test terminal 314 thereof will not be grounded. and therefore no circuit will be provided for the releasemagnet-317 of the connector in posit-ion 2 of the connector steering switch. The arm 318 of the steering switch in moving into position 3 places a ground upon the test terminal 314 of the connector, which causes this line to'test busy to'other connectors, and operates the cutoff relay of the called line to prevent such line from initiating a call. The steering switch in position'3 also closes a circuit for the relay 312 preliminary tothe ringing operation as follows: free'pole of the battery, relayf3l2, conductor 342, conductor 310, arm 309 and third-contact of the" steeringswitch,

conductor 343, conductors 340, 341, arma ture and front contact of relay 305 to ground The relay 312 at its right-hand tact, conductor 340, conductor 341, armature and front contact of calling line relay 305 to ground, or if the battery is at this time connectedbycommutator 328 with conductor 329,-- a direct current circuit from said battery is clos'ed' to the called line.-

, It will be apparent that the cutoff relay of the called line is operated invariably before-the ringing current is applied, since the circuit for said cutoff relay is closed by the arm 318 arriving on' its third contact before the relay 313 can close its front contact to complete vthe ringing circuit, since its circuit is not closed until the relay 312 closes its frontcontact, thus preventing an accidental energizationof the line relay which would look up and uselessly' start a line finder in motion.

Upon'the response of the called party, the

marginal relay 330 opens the circuit of the relay 313, which in turn, at its armature and front contact, opens the ringing circuit and by its denergization moves the steering switch 'intopo'sition 4", in which position the talking cir'cuit is connected through from the calling to the called party. It will be noted that a momentary accidental energi zation of themarginal relay 330 and consequent momentary opening of the circuit of relay 313 would not cause said relay to open the ringing circuit, since relay 31.3 is slowacti-ng.

Battery is fed to the calling party through the line relay 305 and to the called party through the line relay 301, the condensers 353, 354 being interposed in the line conductors 326, 355 between the bridges containing the relays 301, 305.

Upon the conclusion of the conversation, assuming that the calling party is the first to hang up his receiver, the relay 305 becomes deenergized and closes a circuit to release the selector and finder. The finder release circuit is as follows; free pole of the battery, release magnet 203 (Fig. 2), contact 262, conductor 263, right-hand armature and back contact of relay a, conductor 264, conductor 259, arm 258 and its third contact, conductor 254, brush 248 and contact 251, conductor 255, left-hand armature and front contact of relay 301, conductors 344,

right-hand armature and front contact of relay 303, which is slow to release its armature and thus holds this contact closed momentarily after relay 305 releases its armatures, conductor 304, armature andback contact of relay 305 to ground. The selector release circuit is as follows: free pole of battery, release magnet 261, offnormal contact 260, conductor 259 and from this conductor over the circuit previously traced to ground at the armature and back contact of relay 305.

Upon the hanging up of the receiver by the called party, the relay 301 is de'e'nergized and at its right-hand armature and back contact closes a circuit for the release magnet 317 of the connector as follows: free pole of the battery, right-hand winding of the release magnet 317, conductor 346, right hand armature and back contact of relay 301, conductor 322, ofi:'-normal contact 321, conductors 320, 347, left-hand armature and back contact of relay 303, conductor 324, conductor 348, left-hand armature and back contact of relay 301, conductor 302, righthand armature and back contact of relay 303, conductor 304, right-hand armature and back, contact of relay 305 to ground.

The finder, selector and connector switches in restoring, also restore their associated steering switches. In case the calling party fails to hang up his receiver, the called party by opening and closing his line circuit in his next attempt to establish a connection will cause a lamp 349 to flash, the circuit of the lamp leading through the armature and back contact of the called line relay 301. An attendant may then manually release the connector and free the called line.

Fig. 4 shows more clearly the arrange ment whereby a line finder having been started in motion by the initiation of a call cannot be interfered with by the initiation of a call in any other line of any group.

Associated with the relays 0, b of each group of lines is a relaya. Each of these relays a when energized opens at its righthand armature and back contact the circuit of the release magnet 203 of the associated finder. When the steering switch of the finder of line group No. 1 moves to position 3, arm 200 thereof extends the starting conductor 129 to conductor 270, which leads through back contacts of the relay 5 of the next line group to the driving magnet of the line finder normally associated with said group, or if such finder is busy its arm 412 and third contact extend the starting conductor 129 by way of conductor 413 and armatures and back contacts of relay 5 to arm 418, and thence to the finder normally associated with this group of lines.

Assuming now that a second call is initiated in the first line group and that the finders normally associated with the first three line groups are busy. Under such conditions the arms 200, 412 and 418 of their steering switches will be in their third positions, extending the starting conductor 129 through to the driving magnet of the finder normally associated with the fourth group of lines. The relay 131 upon its energization, due to the closure of the line circuit upon the initiation of a call at the substation connected to conductors 401, 402, closes a circuit for the group relay 0 to start the preselected finder. This finder is the fourth one from the left shown in Fig. 2. The circuit is as follows: free pole of battery, left-hand winding of relay 131, conductor 405, left-hand armature and back contact of cutoff relay 132, conductor 406, contacts 403, 404 of relay 131, conductor 407, contacts 408, 118, conductor (Z, lefthand armature and back contact of relay a, conductor. 134, relay. 0 to ground. Relay 0 thereupon becomesenergized and closes the circuit of slow-acting relay Z), which at its right-hand armature and front contact closes the driving circuit to the preselected line finder as follows: ground, right-hand armature and front contact of relay 0', conductors 127, 128, right-hand armature and front contact of relay 6, conductor 129, arm 200 and third contact, conductor 270, lefthand armature and back contact of relay b conductor 410, righthand armature and back contact of relay b conductor 411, arm 412 and third contact of the steering switch of this finder, conductor 413, left-hand armature and back contact of relay b conductor 414, righthand armature and back contact of relay b conductor 421, arm 418 and its third contact, conductor 415, left-hand armature and back contact of b, conductor 416, righthand armature and back contact of relay b conductor 417, arm 419 and its first contact, conductor 420, which leads to the free pole of battery, through the driving magnet 205 of the line finder.

Since arm 419 and conductor 420 of this finder correspond exactly to arm 200 and conductor 201 of the finder of the group normally in operative relation to the group initiating the .call in question, .the circuit may 'becontinued (Fig. 2') :as "followsaconductor 202, right-hand armature and back contactof magnet 203, conductor204, armature and back contact of magnet 205, conductor 206, conductor .268, armature and back contact of relay207, conductors 208, 209, arm210, conductor 275, conductor 212, magnet 205 to free pole ofthebattery. The magnet205 of the fourth finder :referred to, interrupts its own circuit, thus rotating its brush rod until its arm'27 7 contacts with the metallic segment .278 corresponding' to this lineigroup. A ground was placed on this segment 278 at thesright-hand armature and front contact of relay by way of conductors 127 130 and 279. When the arm 277 engages this segment a circuit for the escapement magnet 217 of thiszfinderisclosed to. cut the rotary driving magnet out :of circuit and cut in the'vertical magnet 207 of such finder. This circuit may be traced by way ofcontact27 8, arm 277, to aconductor 283 of this finder, which corresponds to conductor 215, through an arm correspondi ing-to arm 216 of the finder'circuitof Fig.

2, conductor 218, 'escapemen't magnet 217,

magnet 205 to free 'pole-ofb'attery. It will thus be seen that the relay 205 remains attracted on the last impulse, thus positively positioningthe brush M507 and preventing overthrow thereof. From this point on, the operation is 1 the same as .that already traced.

"When therelay 5 closed at its right-hand armature and front'contact the circuit just traced to the rotating driving magnet of the. said finder, it closed at its left-hand armature and front contact a circuit forsthe relays a, a a a. One of these relays is tion of relay 0, which in turn is deenergized by the operation of the cutofi relay ofithe calling line, it will be apparent that the release circuits .for the :finders, it'hrough whose steering switches the starting circuit passes,

l of the selector is bridged around the said cannot be closed until the finder which has been set in motion has reached the =calling line. These relays are then immediately released by the deenergization ofsrelay 0, and consequent denergiz ation of relay b Any finder may be controlled in case of simultaneous calls to stop upon the calling line terminals nearest the normal position of its brushes or farthest fromthe normal position. It is preferred to arrange the circuit so that the finder brushes in case of simulta-- of' finder terminals of the group representing these lines, to the armature 404 and back contact-of line relay 131 of line No. 9, and so on. It will thus 'be evident that when line relay 116 becomes energized and opens contacts 408, 118, it removes the relay 0 from the control of the remaining line relays, and that if, say, line relay N0. 10

should become energized after relayc had been energized and starteda line finder,but before such finder had reached the terminalsgof the line initiating such call, these terminals would be passed over by the linev finderbrushes since the relay of is held energized by a'circuit closed at contacts 117, 1-18 of line relay of'line No. 10, and can not be-deenergized untilthe finder brush'es reach the cutofl relay of this line and deenergize said line relay and consequently relay 0.

In order to prevent sparking at the c0nmary and secondary magnets, a condenser 274 is provided which is connected through the armature and back contact of the release magnet 261 of the selector and conductor 275 to thearm 210 of the finder steering switch. This arm in position 1 of the steering switch'bridges said condenser around the primary magnet 205, and thus prevents sparking at the armature and back contact of said magnet. The arm 210 in movingto position 2 "upon completion of the primarymovement, bridges said condenser around the secondary magnet 207. Upon the completion of the secondaryoperation of the line finder the steering switch arm in position 3 bridges said condenser around primary magnet 236 of the selector. Upon the first upward movement of the selector the spring 237 is shifted from its bottom to its top contact, thus bridging said condenser around the secondary magnet of the selector. Upon the release of the selector and finder switches, this condenser at the armature and front contact of release magnet 261 magnet winding, and the winding of release magnet 203 of the finder which is at this moment in parallel with magnet 261. By "this arrangement the same condenser serves for all six magnets;

. The system can very easily be enlarged by the addition of group selectors between the selector shown and the connector. The circuit of any group selector would be exactly tacts, due to the" self-induction of the prilike that of the selector shown in Fig. 2 with the exception that the arm 210 would not be present in the circuit of conductors 275, 280, as shown by the dotted line.

A contact 281 is associated with the selector brush rod in such a manner that it will be closed if the selector brush rod is given a movement exceeding ten steps. 7 The closure of this contact closes a circuit for the release magnet 203 ,as follows: free pole of battery, release magnet 203, off-normal contact 262 closed upon the first rotary or vertical movement of the brush rod, conductor 282, off-normal contact 281 to ground. This prevents a finder from being held in an offnormal position if for anyreason it failed to be arrested upon arriving on the calling line terminals.

Referring back to that point in the operation where the brushes 221, 222, 228 of the finder are wiping over the contacts of the group containing the calling line to con- 1 nect with such line, .it is possible that at the instant the test brush 223 is passing over the test contact of a non-calling line in such group, a connector may be testing the test terminal of thisnoh-calling line, which is on the same metalstrip 500. The release magnet of the testing connector might in this event receive enough current for its energization, and the consequent release of such connector would give a false busy test to the calling party of that connection. To prevent this a resistance27 2 is included in conductor 271. V

A stepping circuit for the primary mag net 205'leads through the armature and back contact of the finder release magnet 203 for the purposeof preventing a ground, placed upon conductor 129 by the initiation of a call, from completing the circuit of said driving magnet while the finder is releasing.

"What is claimed is:

1. In a telephone exchange system, the combination with telephone lines, of a finder switch having a fixed terminal for each line and a traveling contact adapted to engage said terminals successively, means operated by the initiation of a call in any of said lines for operatingsaid finder switch, relays individualt-o the lines, circuits for successively operating said relays completed by the finder switch as its traveling contact reaches the terminals of said lines, and means permanently associated with said lines and actuated by the'relayl of the calling line to stop the finder switch upon the calling line terminal.

2. In a telephone exchange system, the.

combination'with telephone lines, of a finder switch having a fixed terminal for each line and a traveling contact adapted to engage said terminals successively, a line relay and a cutoff relay for each line, means actuated by any line relay when operated to cause sively operating said cutoff relays completed 'said traveling contact to move over said fixed terminals, and circuits for successively operating the cutoff relays of the lines as said contact brushes wipe over said terminals, and means permanently associated with said lines actuated by the operation of the cutoff relay of the calling line for stopping said traveling contact.

3. In a telephone exchange system, the combination with telephone lines, line relays therefor, a finder switch having a terminal for each line and a traveling contact adapted to engage said terminals successively, means for driving said finder switch actuated under control of any of said line relays upon its energization, a cutoff relay for each line, a

.circuit for controlling said driving means including the back contact of the cutoff relay of the calling line, circuits for succesas said traveling contact reaches the terminals ofsuccessive lines, the cutoff relay of the calling line in opening its back contact disabling said driving means to stop said finder on the calling line.

4. In a telephone exchange system, the combination with telephone lines, of a finder switch wherein said lines terminate, means controlled by any of said lines for causing said finder switch to move, a relay common to and permanently associated with said lines for causing said finder switch to. stop, and a circuit closed when the finder reaches the calling line for actuating said relay.

5. In a telephone exchange system, the 100 combination with telephone lines, line relays therefor, a finder wherein said lines terminate, a group relay, a circuit therefor closed by any line relay when operating, a driving circuit for said finder closed by said group 5 relay, a locking circuit including said line 6. In a telephone exchange system, the

combination with telephone lines, a cutofi relay for each line, a finder switch having fixed terminals for each line and traveling contacts adapted to engage said terminals. a driving magnet for said finder, a circuit for controlling the same including a back contact of the calling line cutoff relay closed 1% upon the initiation of a call in such line, and circuits for successively operating said cutoff relays closed in traveling contacts of said finder as it passes over the line terminals. the

operation of the cutoff relay of the calling 5 line opening said control circuit to stop the finder.

7. In a telephone exchange system, the combination with telephone lines, finder switches, terminals for said lines arranged 1-33 ingroups andtraveling contacts adapted to 'engagethe same, driving circuits {for said finders,,arelay commonto agroulp adapted when operated to close'the driving circuit of one of said ifinders, a relay for each line adapted to, operatesaid group relay, a looking circuit for said line and group relays, a cutoff relay for eachline,'circuits for suc- Qcessively operatingsaid cutoff relays closed icontacts of said findeiflswitches, the operaby the engagement of the traveling and fixed said group relay opens the finder driving 1 combination withsubscriber s lines, line relays "therefor, afinder; having terminals for -said-lines and traveling contacts adapted ,to engage said terminals successively, adriving"c1rc u1t for said-finder, a local circuit closed. by theenergization of any line relay, {a relay operatedby the closure thereof for closing said driving circuit, and relays individual to the lines; and operated success vely as the traveling cont-act's engage said terminals, the relayof the calling line opening said local circuit to stop the finder.

r P 9.="In a telepho'n'e exchange system,--the combination Witl1 ,telfephone lines, a plurality of stationary terminals .to which [said lines are multipled, traveling c'ontactsatdifferent multiple positions 'for engagement with the terminals of said lines, nieans'for setting the traveling terminalsiin motion upon the inistr'ucted and arranged to cause said travelf ing terminals in case simirltaneo'us calls to make ;connection (with the stationary terminal farthest ,from; the normal position 7 of the I traveling tenni'nalf L-IQL-In ,a telephone' exchange system, the

combination yi ith telephone 'Iines'fof a finder switch having term nals ofsaid lines an ranged in a row and aytraveling contact member adapted to' wlpe over'the' same,- l ne relays for said l nes, a driv ng circuit "for I sai d finder, a relay 'a'dapted .to close the same verse'order from that in Which the terminals of the corresponding-linesare engaged by 1 i i idle finder through off-normal 'contacts'of "ll [1n a telephone s'ystempa plurality of Y traveling contactadapted to engage stationary contacts in a definite-order, a "startand a circuit for saidrelay leading thrdrigh the back contacts of'said; line relays in re the traveling Contact member.

lines, l st-at ionai'y contactsfor said 'lines, a

mg circuit "for the; traveling contact, A line relay for; eachline', impacts for said line relays serially incliided said starting circuit in the opposite ordenfromthat in ivhich the stationary contacts are engaged by the traveling contacts, and means to interrupt 7 lithe series starting circuit upon engagement ,tiation ofcalls insaid"lines", and means con-.

1 connectingiwith tl1e' cal1ing :line;

' of the traveling contact with the stationary contact of a-caslling line. a i

12. In a telephone exchange system, the vcombination With a plurality of lines,gline relays therefor, afinder: having passive-terminals-for each line and travelin contacts adapted-t0 engage said termina s successively, .a relay commonttmtheagroup and energized by any line relay to operate the -:finde'r, a locking circuit 'for said: relay to,

maintain the finder in motion, cutofii-elays for said llnes any one ofwhich .maycontrol said drlving c1rcu1t,-and OllCllltSifOl said cutoff relays completed in contacts ot/the line finder as its traveling contacts pass over i said terminals, the said locking circuit in case'of simultaneouscalls.in the same group being opened by thecutolf relay of theialine Whose terminals ,are farthestii'rom thefnora call for closing the driving circuit oftsaid -finder, said circuit leading through .ofiinormal contacts associated With-busy line gfinders', and meanstfor preventing the interruption of'the continuity of said extended drivlng clrcult at said off-normal contacts until [said finder connects Lwith the calling line. i

' "14. In a telephone system,the combination with telephone lines, finders to which said *lines are multipled, driving circuits therefor, l means for preselecting one of fsaid finders, meansactuated upon the initiation ofacall for closing the driving circuit'of saidfinder,

said circuit leading through off-normal contacts associated with busy line-finders, re-

lease circuits for sai d finders, and means ifor mainta nlng the release circuits of said busy findersopen While said preselected lfinder is 15. In a telephone system, the combination with-telephone :lines,;finders to which said lines .are multipled. driving circuits 1 therefor, means actuated upontheinitiation of a call fonclosing the driving circuit v'ot,

said finder, a steering switch-for each lfinder, said dr ving clrcuit leadlng to' av preselected and means for operating the relays of busyv line finders to maintain said release circuits open While the said preselected finder is connecting with the calling line.

16. In a telephone syste1n,"the combina tion with a plurality of lines, selector ing and called line relays at the final one of said switches, a slow-acting relay energized by the operation of said calling line relay, means for maintaining said line relays energized during conver ation and for deenergizing the calling line relay at the termination of the conversation, and a release circuit for the switches preceding the final switch closed momentarily upon the deenergization of said calling line relay and including a back contact of said relay and front contacts of said slow relay and called line relay.

17. In a telephone system, the combination with a plurality of lines, selector switches for interconnecting the same, calling and called line relays at the final one of said switches, a slow-acting relay energized by the operation of said calling line relay,

means formaintaining said line relays energized during conversation and for deenergizing the calling l1ne relay at the termination of the conversation, a release c1rcuit for the switches preceding the final switch closed momentarily upon the deenergization of said calling line relay and in cluding a back contact of said relay and front contacts of said slow relay and called line relay, and a release circuit for the connector closed by the deenergization of'the called line relay and leading through a back contact thereof and back contacts of said called line relay and saidslow-acting relay. W

18. In a telephone system, the combination with metallic circuit telephone lines, a connector having fixed line and test terminalsfor said lines, means controlled over circuits includmg said l ne conductors 1nseries for setting the connector brushes on said terminals, a release magnet for said connector, a steering switch controlling said connector and having a test position wherein the test contact of' the selected line is connected'with sald release magnet, a slow-acting magnet adapted to move said steering switch upon its deenergization, means for deenergizing said magnet when connection is made with the selected line to move said switch out of thetesting position, and circuit for said release magnet including the test contact of the selected line and a contact of said steering switch, said circuit be ing closed before the said magnet moves the saidswitch out ofthe testing position if the selected line is busy.

19. In a telephone system, the combination with telephone lines, automatic switches adapted to interconnect the same including a connector having fixed line and test terminals for said lines, release magnets for said switches, means for setting the connector brushes on said terminals, a steering switch controlling said connector and having a test position wherein the test contact of the selected line is connected with said connector release magnet, a slow-acting mag net adapted to move said steering switch upon its deenergization, means for deenergizing said magnet when connection is made with the selected line to move said switch out of the testing position, a circuit for said connector release magnet including the test contact of the selected line and a contact of said steering switch, said circuit being closed if the selected line is busy before the said magnet moves the said switch out of the testing position, a high resistance locking winding for said connector release magnet, a circuit therefor closed upon the energization of said magnet and including the release magnets of the preceding selector switches,

and a busy back mechanism, said mechanism being included in circuit with the calling line by said connector release magnet.

20. In a telephone system, the combination with telephone lines, automatic selector switches adapted to interconnect the same including a connector having fixed line and test terminals for said lines, release magnets for said switches, means for setting the connector brushes on said terminals, a steering switch controlling said connector and having a test position wherein the test contact of the selected line 'isconnected with said connector releasemagnet, a slow-acting magnet adapted to move said steering switch upon its denergization, means for denerconnector release magnet including the test,

contact of the selected line and a contact of said steering switch, said circuit being closed if the selected line'is busy before the said magnet moves the said switch out of the testing position, ahigh resistance locking winding for said connector release magnet, a circuit therefor closedupon the energization of said magnet and including the release magnets of the preceding selector switches, a busy back mechanism, said mechanism being included in circuit with the calling line by said connector release magnet and a circuit in shunt of said high resistance winding closed upon the disconnecting act of the calling party whereupon said preceding selector switches are released.

21. In a telephone exchange system in combination with telephone lines, automatic selector and connector switches adapted to interconnect the same, a steering switch associated with each of said connectors and having a numberof positions, means for moving said steering switch to the succeeding position when connection is made with the called line, a circuit closed by said steerupon its operation closes said ringing relay circuit to cause said ringingrelay to connect said source of current tothe called line. i

22. In a telephone system the combination with a telephoneline, a jsource of ringing current and a battery, means for applying ringing current. from said source andlcurrent from said batterywto, said line intel'mittently, alslow acting relay adapted to, close a circuit including said sources of-v current and said line, a marginal ringing cutofl'grelay in said circuit controllingiat a back contact said slow-acting.relay,' and means actuated upon the response of the called. party for maintaining said marginal relaysopen ateda suflicientilength of timeto cause.-,t1 1e. .denergization of said sl 0W:im.agn.et -Which thereupon, disconnects. said; c'urrentssources ,from said line, whereby.amomentaryiopera tion of said marginal, irela'y'. will not cut. .off

saidirin ging current. r r 1 ,In ,agtelephonenexchange .system, the

combination with. telephone: .lines, automatic switches adapted t inter onnect the. s m

' driving.magnets therefor,,acondeQsar, an

,iswitch, ,means for I moving the} same, I terminals for said lines at said switch, an auX-' iliary relay permanently connected to one of means nforiassociating Lsaidicondense with r a plurality oflsaid magnets to. ;prevent spar ingat the contacts thereof.

124. r In a telephonesystem -;the.combination with-telep one lines,- a connecto ihaVi g x d. line and; test, termina s; for said li es,

meansv for, setting the connector brushes, ion. saidtermina1s,.a release mag et; iorsaidconnector, a steering. switchi controlling said.

.,connec.tor and. llaVillga test p itio where in, the test ,COIltilCtiOf the; selected line, is coning m g ad p ed. to move -sa d, stee ing rents oversaid line, a second relaypermaected wit saidrelease agnet, .a1s1oW-actw tc up n it .dc rgiza ion,.ineans 1f.or de'e'nergizing" sa d i magnet when connect o is made. withwth i selected net mov said switch outof th te t ng po ition, a

circuit iorsaidreleas magne includi g he test contact of the-selected. line anda contact ofsaid steering switch, said circuit being closed if the selectedlineis busy: before the said magnet moves the. sadoswitch out of {the-testingposition, said .release; magnet having a :liig sresistancei locking winding closed upon its energization and. including H therelease magnets of-the preceding selector ;for: includingsa'id busy backmechanismin circuit. with the calling line upon the release switches, a busy back mechanism, and means of said connector.

.255, In. a telephone exchange system, the

combination. with telephone lines, automatic ,switches adapted to interconnect the same,

driving and release lnagnets therefor, a condenser, andv means for associatlng said condenser Withthe driving and release magnets of a plurality of said. switches to prevent sparking.

26. In a telephone exchange system,,the'

combination with telephone lines, automatic a steering switch associated with one of said automatic switchesmand having a contact in arm and cooperatlng contacts, driving magnets connected with said contacts, and a condenser, sai d arm being a dapted as it ad- .vances to include saidmagnetsjn circuit and. also bridging said condenser there :around to prevent sparking.

27. A telephone exchange systenrincludvswitches adapted to interconnect the same,

ing a telephone 11116,,21 line relay normally operatively connected therewith and ,individual thereto, means for operating said line relay responsive to currents over said line,

an automaticswitch, multi leterminals pertaining. to said llne atsai sw tch, a second 28. A telephonerexchange system including a telephone line, a line relay normally operatively' connected, thereto, an automatic said terminals andoperated when the switch engages the ternnnal to .WlllCll it is connected, and means actuated by said auxiliary relay in operating for arresting the movemen Jofv saidis itohv 29. A telephone exchange system including 7 a telephone line, a finder, operating .means therefor, .a linea'elay normally 0p- .erat vely connected withsaid line, means foroperating said, line relay responsive to cur operatively connected thereto,.an auxiliary relay permanently associated with said, line, an automatic switch for operat ng said aux- .iliary relay the operation of which deter- ;mines theaction of said automatic switch,

substantially as set forth. a 31. A telephone exchange system including a telephonegline, alpine relay normally 'operatively connected therewith and individual thereto, .means for operating said line relay responsive to currents over said line, a second relay permanently associated with said line, an automatic switch, multiple terminals for said line at said switch, an auxiliary device associated with said relays and brought into action by said second relay to cause said switch when traveling to come into engagement with said terminals, substantially as set forth.

32. In a telephone exchange system wherein calling lines are divided into groups and terminate in a row multipled across the face of a panel, the combination with a carrier for each row, of multiply connected brushes mounted spirally upon each carrier, one for each group of terminals, the carriers being so arranged that each group of lines has a brush normally in operative relation to multiples thereof, and means for moving said carriers independently upon the initiation of calls in said groups.

33. In a telephone exchange system wherein calling lines are divided into groups, multipled to groups of terminals in a number of finders, the combination with the finders, brush carriers therefor, said carriers having a plurality of multiply connected brushes, one for each group, arranged spirally on said carrier, the carriers being so arranged that each group of lines has a brush normally in operative relation to multiples thereof, driving means for said carriers, and means for causing said driving means to move said carriers independently upon the initiation of calls in said groups in search of calling lines.

In witness whereof, I hereunto subscribe my name this 17th day of November, A. D. 1914.

CHARLES L. GOODRUM.

Witnesses E. EDLER, IRVING MACDONALD.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

